Abstract: A single "L"-shaped modular building unit comprises an integral end wall and ceiling and incorporates an outwardly depending flange peripherally surrounding the entire modular unit. The overall ceiling length is equal to twice the ceiling width. The outwardly depending peripherally surrounding flange is rectangular along its exposed edge to provide a modular unit which can be easily interconnected with similar units in any desired arrangement. Along the interior facing edge of the flange, the overall rectangular shape incorporates radii of curvature at the ceiling-wall interface for additional aesthetic purposes. The interconnecting portion between the wall and the ceiling is a saddle-shaped curve extending both longitudinally and laterally substantially the entire length of the ceiling and down a substantial portion of the wall.